Circuit board structure having embedded electronic element and fabrication method thereof

ABSTRACT

A method for fabricating a circuit board structure having at least an embedded electronic element is disclosed, which includes the steps of: providing a substrate and embedding at least an electronic element in the substrate with an active surface and a plurality of electrode pads of the electronic element exposed from a surface of the substrate; forming a plurality of conductive bumps on the electrode pads of the electronic element; and covering the surface of the substrate and the active surface of the electronic element with a dielectric layer and a metal layer stacked on the dielectric layer, wherein the conductive bumps penetrate the dielectric layer so as to be in contact with the metal layer, thereby simplifying the fabrication process, reducing the fabrication cost and saving the fabrication time.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to circuit board structures andfabrication methods thereof, and more particularly, to a circuit boardstructure having at least an embedded electronic element and afabrication method thereof.

2. Description of Related Art

Along with the progress of semiconductor packaging technologies, variouspackage types have been developed for semiconductor devices. Forexample, an electronic element can be embedded in and electricallyconnected to a packaging substrate so as to form a package. Such apackage has reduced size and improved electrical performance andtherefore has become a main trend.

FIGS. 1A to 1F are schematic cross-sectional views showing a circuitboard structure having embedded electronic elements and a fabricationmethod thereof according to the prior art.

Referring to FIG. 1A, a substrate 10 is provided, which has oppositefirst and second surfaces 10 a, 10 b and a cavity 100 penetrating thefirst and second surfaces 10 a, 10 b. An adhesive layer 11 is formed onthe second surface 10 b of the substrate 10 to cover one end of thecavity 100, and a plurality of electronic elements 12 are disposed onthe adhesive layer 11 in the cavity 100. Each of the electronic elements12 has a first active surface 12 a having a plurality of first electrodepads 121 a and a second active surface 12 b opposite to the first activesurface 12 a and having a plurality of second electrode pads 121 b. Thefirst active surfaces 12 a and the first electrode pads 121 a of theelectronic elements 12 are exposed from the first surface 10 a of thesubstrate 10.

Referring to FIG. 1B, a first dielectric layer 13 a is laminated on thefirst surface 10 a of the substrate 10 and the first active surfaces 12a of the electronic elements 12. Further, the first dielectric layer 13a flows into the cavity 100 so as to cover side surfaces of theelectronic elements 12.

Referring to FIG. 1C, the adhesive layer 11 is removed to expose thesecond active surfaces 12 b and the second electrode pads 121 b of theelectronic elements 12 from the second surface 10 b of the substrate 10.Then, a second dielectric layer 13 b is laminated on the second surface10 b of the substrate 10 and the second active surfaces 12 b of theelectronic elements 12. Thereafter, the first dielectric layer 13 a iscovered with a first copper foil 14 a, and the second dielectric layer13 b is covered with a second copper foil 14 b.

Referring to FIG. 1D, a brown oxide treatment is applied to the firstand second copper foils 14 a, 14 b, and a laser drilling process isperformed to form a plurality of first openings 130 a through the firstcopper foil 14 a and the first dielectric layer 13 a to expose the firstelectrode pads 121 a and form a plurality of second openings 130 bthrough the second copper foil 14 b and the second dielectric layer 13 bto expose the second electrode pads 121 b.

Referring to FIG. 1E, a conductive layer 15 is formed on walls of thefirst and second openings 130 a, 130 b by electroless plating.

Referring to FIG. 1F, an electroplating process is performed through theconductive layer 15 so as to form a plurality of first conductive vias16 a in the first openings 130 a and form a plurality of secondconductive vias 16 b in the second openings 130 b, thus electricallyconnecting the first and second copper foils 14 a, 14 b through thefirst and second conductive vias 16 a, 16 b.

However, in the above-described method, the laser drilling, electrolessplating and electroplating processes are complicated, costly andtime-consuming.

Therefore, there is a need to provide a circuit board structure havingat least an embedded electronic element and a fabrication method thereofso as to overcome the above-described drawbacks.

SUMMARY OF THE INVENTION

In view of the above-described drawbacks, the present invention providesa circuit board structure having at least an embedded electronicelement, which comprises: a substrate having opposite first and secondsurfaces; at least an electronic element embedded in the substrate,wherein the electronic element has a first active surface having aplurality of first electrode pads and a second active surface oppositeto the first active surface and having a plurality of second electrodepads, the first active surface and the first electrode pads of theelectronic element being exposed from the first surface of thesubstrate; a plurality of first conductive bumps formed on the firstelectrode pads of the electronic element, wherein each of the firstconductive bumps is bonded to the corresponding first electrode padthrough a bottom portion thereof and the bottom portion is greater inwidth than an opposite top portion of the first conductive bump; a firstdielectric layer formed on the first surface of the substrate and thefirst active surface of the electronic element and penetrated by thefirst conductive bumps; and a first metal layer formed on the firstdielectric layer and the first conductive bumps and in contact with thefirst conductive bumps.

The present invention further provides a method for fabricating acircuit board structure having at least an embedded electronic element,which comprises the steps of: providing a substrate having oppositefirst and second surfaces and embedding at least an electronic elementin the substrate, wherein the electronic element has a first activesurface having a plurality of first electrode pads and a second activesurface opposite to the first active surface and having a plurality ofsecond electrode pads, the first active surface and the first electrodepads of the electronic element being exposed from the first surface ofthe substrate; forming a plurality of first conductive bumps on thefirst electrode pads of the electronic element; and covering the firstsurface of the substrate and the first active surface of the electronicelement with a first dielectric layer and a first metal layer stacked onthe first dielectric layer, wherein the first conductive bumps penetratethe first dielectric layer so as to be in contact with the first metallayer.

Therefore, the present invention dispenses with the conventional laserdrilling, electroless plating and electroplating processes so as tosimplify the fabrication process, reduce the fabrication cost and savethe fabrication time.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A to 1F are schematic cross-sectional views showing a circuitboard structure having embedded electronic elements and a fabricationmethod thereof according to the prior art; and

FIGS. 2A to 2G are schematic cross-sectional views showing a circuitboard structure having at least an embedded electronic element and afabrication method thereof according to the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The following illustrative embodiments are provided to illustrate thedisclosure of the present invention, these and other advantages andeffects can be apparent to those in the art after reading thisspecification.

It should be noted that all the drawings are not intended to limit thepresent invention. Various modifications and variations can be madewithout departing from the spirit of the present invention. Further,terms such as “top”, “bottom”, “end”, “a” etc. are merely forillustrative purposes and should not be construed to limit the scope ofthe present invention.

FIGS. 2A to 2G are schematic cross-sectional views showing a circuitboard structure having at least an embedded electronic element and afabrication method thereof according to the present invention.

Referring to FIG. 2A, a substrate 20 is provided, which has oppositefirst and second surfaces 20 a, 20 b and a cavity 200 penetrating thefirst and second surfaces 20 a, 20 b. An adhesive layer 21 is formed onthe second surface 20 b of the substrate 20 for covering one end of thecavity 200, and at least an electronic element 22 is disposed on theadhesive layer 21 in the cavity 200. In the present embodiment, aplurality of electronic elements 22 are disposed on the adhesive layer21 in the cavity 200. Each of the electronic elements 22 has a firstactive surface 22 a having a plurality of first electrode pads 221 a anda second active surface 22 b opposite to the first active surface 22 aand having a plurality of second electrode pads 221 b. The first activesurface 22 a and the first electrode pads 221 a of the electronicelement 22 are exposed from the first surface 20 a of the substrate 20.The electronic element 22 can be a capacitor, such as a multi-layerceramic capacitor (MLCC).

Referring to FIG. 2B, a plurality of first conductive bumps 23 a made ofsuch as silver paste are formed on the first electrode pads 221 a byprinting and heated so as to be cured. Each of the first conductivebumps 23 a is bonded to the corresponding first electrode pad 221 athrough a bottom portion thereof and the bottom portion is greater inwidth than an opposite top portion of the first conductive bump 23 a.

Referring to FIGS. 2C and 2D, the first surface 20 a of the substrate 20and the first active surfaces 22 a of the electronic elements 22 arecovered with a first dielectric layer 24 a and a first metal layer 25 astacked on the first dielectric layer 24 a. Further, the firstdielectric layer 24 a flows into the cavity 200 to cover side surfacesof the electronic elements 22. The first dielectric layer 24 a and thefirst metal layer 25 a can be made of a resin-coated copper foil. Thefirst conductive bumps 23 a penetrate the first dielectric layer 23 a soas to be in contact with the first metal layer 25 a. Then, the adhesivelayer 21 is removed to expose the second active surfaces 22 b and thesecond electrode pads 221 b of the electronic elements 22 from thesecond surface 20 b of the substrate 20.

Referring to FIG. 2E, a plurality of second conductive bumps 23 b madeof such as silver paste are formed on the second electrode pads 221 b byprinting and heated so as to be cured. Each of the second conductivebumps 23 b is bonded to the corresponding second electrode pad 221 bthrough a bottom portion thereof and the bottom portion is greater inwidth than an opposite top portion of the second conductive bump 23 b.

Referring to FIGS. 2F and 2G, the second surface 20 b of the substrate20 and the second active surfaces 22 b of the electronic elements 22 arecovered with a second dielectric layer 24 b and a second metal layer 25b stacked on the second dielectric layer 24 b. The second conductivebumps 23 b penetrate the second dielectric layer 24 b so as to be incontact with the second metal layer 25 b, thereby electricallyconnecting the first metal layer 25 a and the second metal layer 25 bthrough the first conductive bumps 23 a and the second conductive bumps23 b. As such, a circuit board structure 2 having a plurality ofembedded electronic elements 22 is formed.

The present invention further provides a circuit board structure 2having at least an embedded electronic element, which has: a substrate20 having opposite first and second surfaces 20 a, 20 b; at least anelectronic element 22 embedded in the substrate 20, wherein theelectronic element 22 has a first active surface 22 a having a pluralityof first electrode pads 221 a and a second active surface 22 b oppositeto the first active surface 22 a and having a plurality of secondelectrode pads 221 b, the first active surface 22 a and the firstelectrode pads 221 a of the electronic element 22 being exposed from thefirst surface 20 a of the substrate 20; a plurality of first conductivebumps 23 a formed on the first electrode pads 221 a of the electronicelement 22, wherein each of the first conductive bumps 23 a is bonded tothe corresponding first electrode pad 221 a through a bottom portionthereof and the bottom portion is greater in width than an opposite topportion of the first conductive bump 23 a; a first dielectric layer 24 aformed on the first surface 20 a of the substrate 20 and the firstactive surface 22 a of the electronic element 22 and penetrated by thefirst conductive bumps 23 a; and a first metal layer 25 a formed on thefirst dielectric layer 24 a and the first conductive bumps 23 a and incontact with the first conductive bumps 23 a.

In the above-described circuit board structure 2, a cavity 200 is formedin the substrate 20 to penetrate the first and second surfaces 20 a, 20b, thus allowing the electronic element 22 to be disposed in the cavity200 and exposing the second active surface 22 b and the second electrodepads 221 b of the electronic element 22 from the second surface 20 b ofthe substrate 20. Therefore, the circuit board structure 2 further has:a plurality of second conductive bumps 23 b formed on the secondelectrode pads 221 b, wherein each of the second conductive bumps 23 bis bonded to the corresponding second electrode pad 221 b through abottom portion thereof and the bottom portion is greater in width thanan opposite top portion of the second conductive bump 23 b; a seconddielectric layer 24 b formed on the second surface 20 b of the substrate20 and the second active surface 22 b of the electronic element 22 andpenetrated by the second conductive bumps 23 b; and a second metal layer25 b formed on the second dielectric layer 24 b and the secondconductive bumps 23 b and in contact with the second conductive bumps 23b.

In the present embodiment, the first conductive bumps 23 a are made ofsilver paste. The electronic element 22 is a capacitor, such as amulti-layer ceramic capacitor (MLCC).

Therefore, the present invention dispenses with the conventional laserdrilling, electroless plating and electroplating processes so as tosimplify the fabrication process, reduce the fabrication cost and savethe fabrication time.

The above-described descriptions of the detailed embodiments are only toillustrate the preferred implementation according to the presentinvention, and it is not to limit the scope of the present invention.Accordingly, all modifications and variations completed by those withordinary skill in the art should fall within the scope of presentinvention defined by the appended claims.

What is claimed is:
 1. A method for fabricating a circuit boardstructure having at least an embedded electronic element, comprising thesteps of: providing a substrate having opposite first and secondsurfaces and embedding at least an electronic element in the substrate,wherein the electronic element has a first active surface having aplurality of first electrode pads and a second active surface oppositeto the first active surface and having a plurality of second electrodepads, the first active surface and the first electrode pads of theelectronic element being exposed from the first surface of thesubstrate; forming a plurality of first conductive bumps on the firstelectrode pads of the electronic element; and covering the first surfaceof the substrate and the first active surface of the electronic elementwith a first dielectric layer and a first metal layer stacked on thefirst dielectric layer, wherein the first conductive bumps penetrate thefirst dielectric layer so as to be in contact with the first metallayer.
 2. The method of claim 1, wherein a cavity is formed in thesubstrate to penetrate the first and second surfaces and an adhesivelayer is attached to the second surface of the substrate to cover oneend of the cavity, thus allowing the electronic element to be disposedon the adhesive layer in the cavity, therefore, after covering the firstsurface of the substrate and the first active surface of the electronicelement with the first dielectric layer and the first metal layerstacked on the first dielectric layer, the method further comprises:removing the adhesive layer to expose the second active surface and thesecond electrode pads of the electronic element from the second surfaceof the substrate; forming a plurality of second conductive bumps on thesecond electrode pads; and covering the second surface of the substrateand the second active surface of the electronic element with a seconddielectric layer and a second metal layer stacked on the seconddielectric layer, wherein the second conductive bumps penetrate thesecond dielectric layer so as to be in contact with the second metallayer.
 3. The method of claim 1, wherein the first conductive bumps aremade of silver paste.
 4. The method of claim 1, after forming the firstconductive bumps, further comprising heating the first conductive bumps.5. The method of claim 1, wherein the electronic element is a capacitor.6. The method of claim 1, wherein the stacked first dielectric layer andthe first metal layer are made of a resin-coated copper foil.